RFC 1613 (rfc1613) - Page 2 of 13
cisco Systems X
Alternative Format: Original Text Document
RFC 1613 X.25 Over TCP (XOT) May 1994
length field, which is used to separate the X.25 packets within the
TCP stream.
In general, the normal X.25 protocol packet formats and state
transition rules apply to the X.25 layer in XOT. Exceptions to this
are noted.
2. Conventions
The following language conventions are used in the items of
specification in this document:
o MUST, SHALL, or MANDATORY -- This item is an absolute
requirement of the specification.
o SHOULD or RECOMMEND -- This item should generally be followed
for all but exceptional circumstances.
o MAY or OPTIONAL -- This item is truly optional and may be
followed or ignored according to the needs of the implementor.
In some places in this document, there is parenthetical material
labeled "DISCUSSION". This material is intended to give
clarification and explanation of the preceding text.
3. Relationship Between XOT and X.25
When a networking device (a host, router, etc.) has an X.25 engine
(i.e., protocol implementation), that engine may be connected to
interface(s) running LAPB, and/or to logical interface(s) running LLC
or XOT/TCP/IP. In general, the XOT layer itself is not at all
sensitive to what kind of packets the X.25 engine passes to it.
However, to improve interoperability between separate
implementations, this document in some cases does specify behavior of
the X.25 engine.
While this document primarily discusses XOT from the perspective of
switching X.25 traffic (i.e., connecting an X.25 Virtual Circuit
between the local X.25 interfaces of two networking devices), this
should not prevent a host from offering X.25 connectivity using XOT.
The various X.25 standards may call a given packet type by a
different name according to the assigned DTE/DCE role of the
interface that originated the packet. XOT is intended to be
insensitive to the DTE/DCE role of the local interfaces at either end
of an XOT TCP connection, so, for this document, the following terms
are interchangeable unless stated otherwise:
Forster, Satz, Glick & Day